Continuing Our Search for Bushmasters




Authored by Stephen Spear

Since my last update in the August e-newsletter, I have had the opportunity to make several trips to Costa Rica as part of our Mesoamerican Project focused on bushmaster conservation. Our work up to this point has been focused on searching known areas for these snakes, with the hope that the addition of a camera to search refuges more effectively would better open up the world of the bushmaster. Unfortunately, no matter where or how you search, bushmasters are clearly extremely difficult to find. In fact, a fellow researcher interested in bushmasters told me that he thinks a rough estimate for the rate of finding bushmasters in Central America to be around one for every 100 days of searching! With this is mind, much of our recent work has been focused on trying to adapt to these circumstances by modifying our strategy beyond (but still including) field searches.


One of these strategies is to coordinate more directly with local residents who would report any sightings to us and who might be willing to conduct independent searches on their own (and keep track of their search time). This idea is really appealing to us not only because it will increase search time, but also because we believe it will help demonstrate that bushmasters are valuable and of interest, therefore reducing persecution when they are encountered. In return, we can provide them with the necessary tools, such as GPS units and digital cameras. My trip in December was primarily centered on this goal. Working with our project partner Guido Saborio, we visited a number of sites that demonstrated promise for working with local residents. These ranged from places that we had visited before and already had a good relationship with owners to spots where we had heard anecdotal reports.

Below I highlight a couple of examples of what we’ve done with some of those anecdotal reports.


One instance was a shrimp farm near mangrove wetlands where Guido had heard reports that workers there had seen Black-headed Bushmasters. Guido and I both initially thought this an unlikely spot for bushmasters, as we associate them with more upland habitat, but we had also seen a recent paper that reported historic bushmaster sightings in the area. So we decided it was worth a visit. We drove through a maze of oil palm plantations until we came to the gate of the shrimp farm. We hadn’t been able to reach anyone to tell them of our visit, so we weren’t completely sure if they would grant us access to talk to people at the farm. But once we explained that we were there to ask about big snakes, the guard radioed the manager who told him to let us come into the farm. The manager on duty told us the workers were all busy, but if we wanted to come back at night, they could show us areas where the snakes had been seen.


When we went back that evening, we went out with the workers. As I walked around the ponds watching eye-shine of crocodiles passing back and forth, Guido quizzed the guards and showed them photos of snakes on his phone. Pretty soon, Guido realized what the “bushmasters” likely were. Tree Boas (Corallus ruschenbergerii) are common residents of mangrove forests, and apparently someone had told one of the workers that these snakes in the trees were bushmasters. Although it didn’t turn out to be a productive lead for bushmasters, our visit yielded some benefits. First, the workers now know the snakes in the trees are harmless. Second, we had a request from the manager to give a talk to the workers about snake identification and snake safety, an opportunity we will definitely take advantage of in the coming months.


However, we did make several connections that should have greater potential for finding bushmasters. On a previous visit, I talked to someone from a local private sanctuary who seemed interested in what we want to do for snakes in the area. He is one of three brothers that run Santuario Gamba Gam near Golfito; Guido was acquainted with them as well, so we arranged a visit to their property. While the brothers had not seen bushmasters on their property, the sanctuary is near sites where we know bushmasters have been encountered—in fact, one of their workers had seen them in the area where he was from and was willing to help us plan a future trip. We left Gamba Gam with a new partner, and we look forward to working with them and coordinating with other residents in the area to understand the status of bushmasters there.


Another connection we made on the December trip was with Reinaldo Aguilar, a botanist who has discovered many new plant species on the Osa Peninsula. Guido already knew Reinaldo, but I asked about him when a picture that he had taken of a Black-headed Bushmaster was forwarded to me. That was the only bushmaster Reinaldo had seen, but he was very enthusiastic about working with us and immediately wanted to plan a trip into an area he knew well and is known for the presence of plato negro (the local name for the bushmaster). Reinaldo is passionate about conservation of the entire Osa ecosystem, and I think he sees the bushmaster as another flagship species to gather support for this wonderful region.

When I said Reinaldo wanted to immediately go out with us, he wasn’t joking. A month after our conversation in a Puerto Jimenez coffee shop, I went back to the Osa for a January trip. In addition to Guido and Reinaldo, I was joined by Marcelo Carvajal (another snake expert that has joined us for several of these adventures) and three guides that Reinaldo knows and who have seen bushmasters in the area. We also had two horses to help pack in our gear. While I like to backpack as much as anyone, my last backpacking experience in the Osa was a rainy season march through Corcovado that I still have scars from, so I was happy for the help this time!

On the first day, after our arrival in camp, the guide who led the horses (we took a different route) told us he thought he saw the plato negro. Wait, what? As it turns out, as he was riding the horses up, all of a sudden the horses refused to go forward, which apparently is a common horse reaction to snakes (or so I was told). He said he heard a loud rattling near a log and saw a large vibration through the ground cover. He didn’t get off the horse while this was happening, but he marked the spot for us to check. The spot was a little too far to go to that night, but the next morning we hiked there. Sure enough, underneath the large log across the trail, there was a large rounded and smoothed-out patch, very consistent with a snake. A thorough search of the area did not yield a snake, but we are very confident that a big snake was there, and a Black-headed Bushmaster would be on the short list of suspects.

Another positive experience from that trip was our interaction with one of the guides who was very excited about snakes but didn’t know a lot. He came out with us as we looked for snakes, getting to see species like White-tailed Hognose Vipers (Porthidium porrasi), Graceful Brown Snakes (Rhadinaea decorate) and Salmon-bellied Racers (Mastigodryas melanolomus). At the end, like the shrimp farm workers, he asked if we could teach him about the different types of snakes in the area. One thing we will definitely be bringing with us in the future are ID sheets highlighting Osa snakes!

While we still have a lot of work to do, I am excited about the connections we are making and the interest we’ve had in targeted searches to help us learn more about these threatened vipers. In the next few months, we are going to follow up on these promising areas and continue our mission to encourage positive snake awareness on the Osa.